I have the samsung SIR series2 DirectvTivo

In the past I have bought and ran instantcake for 6.2, which has automatically upgraded to 6.4 as time went on.

I finally bought ptvnet so I could set up the MRV on my 3 tivos and I have got them all working with the HMO, but MRV just does not work. There are confusing posts all over the place regarding this, but it looks like I'm going to have to go back to 6.2 to make it happen.

Questions:

1. will going back to 6.2 on these boxes be a problem to activate, or since it's the same card and machine, it will be easy?

2. once I have 6.2 reinstalled, how do I prevent the updates that make it 6.4a?